When having cold or hot stuff and/or sweet or sour stuff in the mouth, people sometimes feel acute electrical tooth pain. This is generally called hypersensitivity, and this occurs when gums become thinner due to, for example, periodontitis and the dentin of a tooth root is then exposed and/or when enamel is damaged and the dentin is then exposed. Accordingly, this is also called dentin hypersensitivity. This dentin hypersensitivity is believed to occur when dentinal tubules on the surface of dentin have openings and physical and chemical stimulation such as brushing and/or temperature stimulation is given to the openings. However, there have been various theories on the mechanism of its onset and the mechanism is thus not fully understood. Nowadays, the “hydrodynamic theory,” in which brushing and/or temperature stimulation, for example, is given and the internal fluid of dentinal tubules then moves, seems to be plausible.
In addition, during bleaching treatment so as to effectively achieve beautiful appearance, there is a concern about the hypersensitivity problem. Hence, a method for inhibiting dentin hypersensitivity has been sought.
Some dentinal tubule occlusion methods, one means for inhibiting the dentin hypersensitivity, have been proposed, including: for example, a method (Patent Document 1) using a dental therapeutic agent for hypersensitivity, the agent comprising an acidulated phosphate fluoride-tannic acid solution component, a lanthanum chloride aqueous solution component, and fluoroapatite-based glass powder; and a method (Patent Document 2) using a therapeutic agent for dentin hypersensitivity, the agent consisting of an oxalic acid compound solution and a calcium compound solution. Other dentinal tubule occlusion methods using hydroxyapatite have also been proposed, including: a method (Patent Document 3) using a composition for hypersensitivity, the composition using hydroxyapatite with a particle size of from 1.0 μm to 5.0 μm; and a method (Patent Document 4) using a sealant for dentinal tubules while sintered hydroxyapatite particles with a particle size of 900 nm or less are used for the dentinal tubule sealant.
Further, the following has been proposed, including: a hypersensitivity-inhibiting dentifrice (Patent Document 5) comprising potassium nitrate and stannous fluoride as an oral composition using potassium nitrate that functions as an agent for alleviating and inhibiting hypersensitivity; an oral composition (Patent Document 6) in which amino acid and a salt thereof or nucleic acid and a salt thereof are blended in an oral composition comprising potassium nitrate; an oral composition (Patent Document 7) comprising specific concentrations of a potassium salt and an aluminum salt; and an oral composition (Patent Document 8) in which potassium nitrate and reduced palatinose are blended.
Meanwhile, calcium monohydrogen phosphate dihydrate (dibasic calcium phosphate) is used as, for example, a base material for dentifrice, a cleaning agent, or a polishing agent. Some oral compositions using calcium monohydrogen phosphate dihydrate have been proposed, including: for example, in order to remove plaques on the surface of a tooth to increase whiteness of the tooth, a dentifrice composition (Patent Document 9) comprising aggregated particles selected from calcium carbonate, dibasic calcium phosphate, tribasic calcium phosphate, calcium pyrophosphate, and hydroxyapatite, the particles having an average particle size of 3.5 to 10 μm and a disintegration strength of 0.1 to 5 g/particle; and in order to effectively remove tooth colorants without significantly damaging a tooth, a dentifrice composition (Patent Document 10) comprising: granules having an average particle size of 100 to 500 μm and a disintegration strength of 0.1 to 10 g/granule, the granules being prepared using powder as a polishing agent such as dibasic calcium phosphate, tribasic calcium phosphate, calcium pyrophosphate, magnesium phosphate, insoluble sodium metaphosphate, silica, hydroxyapatite, aluminum hydroxide, alumina, calcium carbonate, magnesium carbonate, calcium sulfate, zeolite, an aluminosilicate complex, and red iron oxide; and at least one polishing powder selected from zeolite, calcium carbonate, dibasic calcium phosphate anhydride, tribasic calcium phosphate, hydroxyapatite, and aluminum hydroxide, the powder particles having a Mohs' hardness of 2 to 6 and an average particle size of 0.5 to 5 μm.